This invention relates generally to biological liquid filtration systems and methods. More particularly, this invention relates to a non-vented gravity driven biological liquid filtration system and method usable to collect, filter and store biological liquids such as blood or blood components.
Typically, blood filtration systems allow unfiltered liquid to remain within the filtration system after filtration has occurred. This remaining unfiltered liquid, referred to as a hold up volume, is often greater than the desired maximum amount. As discussed below, applicant has discovered that this will be particularly true in an in-line, closed system that does not use gas vents to aid in recovery of unfiltered liquid. Also, conventional blood filtration systems do not limit the interface of gas with biological liquid in the system to provide a more consistent and safe processed blood product, nor do they provide as simple and as automatic a system as the present invention.
Certain blood filtration devices are disclosed in the following patents or applications: U.S. Pat. No. 5,472,605, entitled xe2x80x9cA Filtration Device Usable for Removal of Leukocytes and Other Blood Componentsxe2x80x9d issued Dec. 5, 1995; U.S. Pat. No. 5,798,041, entitled xe2x80x9cAn In-Line Liquid Filtration Device Usable for Blood, Blood Products and the Likexe2x80x9d; U.S. Pat. No. 6,010,633, entitled: xe2x80x9cIn-line Gravity Driven Liquid Filtration Device Usable to Filter Blood or Blood Productsxe2x80x9d issued Jan. 4, 2000; U.S. Ser. No. 09/260,967, entitled xe2x80x9cSystem and Method of Filtering and Collecting Blood or Blood Productsxe2x80x9d filed Mar. 2, 1999, abandoned; and, U.S. Ser. No. 09/133,245, entitled xe2x80x9cImproved Flow Distributor and Method for Use with a Filter Devicexe2x80x9d filed Aug. 13, 1998, abandoned, and these all are incorporated by reference and made a part of the disclosure herein. Filtration methods using these types of devices rely upon, at least in part, a vented system to maximize the recovery of blood or blood product upstream of the filter. Because of such a venting feature, at least in part, these prior art devices are unlike the present invention, although they are similar in other respects except as discussed hereafter.
Conventional teaching in the art of blood filtration suggests that such filtration systems can have only 5 ml or less of gas per bag in any bag of the blood collection systems, i.e., upon set up of the system. This is according to the 1997 ISO 3826 practice, which is industry practice prior to and at the time of applicant""s invention. Additionally, conventional teaching in the art suggests that gas and blood interfacing in the system is not desirable due to potential damage to blood constituents, and the longer the time of interface the more likely that gas-borne contaminants may get into the blood. Finally, it is known that an increase in recovery of only 1-2% of the total biological liquid processed in a system (e.g., due to hold up volume) may make a large difference in the art. In fact, International Regulations require that a system have at least 85% recovery and typically 90% or above. Moreover, the recovery rate of 85% is required for 100% of the systems used.
In light of the foregoing, it may be desirable to obtain a liquid filtration system and method that enhance the recovery of biological liquids, especially in a non-vented biological liquid filtration system. Also, it may be desirable to operate any such system as automatically as possible to reduce the need for human intervention (e.g., eliminating squeezing of containers in the system when transferring container contents) and to cause liquid processing to occur merely under a force of gravity and/or atmospheric pressure or other natural environmental forces acting in or upon the system. Further, it may be desirable to limit the time and amount of exposure of gas in the system with the biological liquid being processed.
The shortcomings of the prior art may be alleviated and the aforementioned goals may be achieved by using a filtration system and method in accordance with one or more principles of the present invention. The filtration system and method of the present invention is useable when filtering blood or blood components to remove leukocytes, other blood components, cells, or chemical agents which may be used to treat the blood. Additionally, other uses may be made of the invention which fall within the scope of the claimed invention but which are not specifically described below.
In one aspect of the invention, there is provided a filtration system and method for the filtration of a biological liquid such as blood or blood components. The system includes a biological liquid collection assembly, a filtration assembly in communication with the biological liquid collection assembly and a blood components preservative assembly in communication with the biological liquid collection assembly. The blood components preservative assembly includes a blood components preservative container and the blood components preservative container may contain a blood components preservative solution and contains a measured quantity of a sterile gas. The blood components preservative assembly is adapted to automatically transfer at least a portion of, respectively, the blood components preservative solution, if present, and the sterile gas to the biological liquid collection assembly under a force of gravity once fluid flow communication is commenced between the blood components preservative container and the biological liquid collection assembly.
In another aspect of the invention there is provided a method for processing biological liquid in said filtration system. The method includes providing the biological liquid in the biological liquid collection container and automatically transferring at least a portion of, respectively, the blood components preservative solution, if present, and the measured quantity of the sterile gas into the biological liquid collection container under the force of gravity. Further, the method may include automatically transferring at least a portion of, respectively, the biological liquid, the blood components preservative solution, if present, and the sterile gas under the force of gravity to a biological liquid filter downstream of the biological liquid collection container and collecting the biological liquid and blood components preservative solution, if present, that have passed through the biological liquid filter into a biological liquid storage container.
Yet other aspects of the invention concern: a satellite bag assembly in communication with the biological liquid collection assembly; particular configurations for connecting various components of the system; and, particular attributes of certain components of the system, all which can enhance safe and efficient use of the system, as desired.